The aim of the work proposed here is to identify and characterize the integral cell surface molecules involved in two types of adhesive processes in epithelial cells--cell-cell and cell-substratum adhesion. The approach is to use broad spectrum antisera which specifically and reversibly disrupt these two types of adhesive complexes. A blocking assay has been developed to allow the identification of the antigens with which the antisera interact. This enables us to purify the molecules of interest from NP-40 extracts of mouse mammary tumor epithelial cells. Monoclonal monospecific antibodies will be produced by making hybridomas from rats injected with the purified constituents. Ultrastructural and genetic studies will serve to localize the molecules of interest on the cell surface and confirm their role in one of the adhesive reactions. Molecules will be characterized both biochemically and serologically. Detailed preliminary results are included.